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/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch licenses this file to you under
 * the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.elasticsearch.search.aggregations;

import org.elasticsearch.common.bytes.BytesReference;
import org.elasticsearch.common.io.stream.StreamInput;

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import static java.util.Collections.emptyMap;
import static java.util.Collections.unmodifiableMap;

/**
 * A registry for all the dedicated streams in the aggregation module. This is to support dynamic addAggregation that
 * know how to stream themselves.
 */
public class AggregationStreams {
    private static Map streams = emptyMap();

    /**
     * A stream that knows how to read an aggregation from the input.
     */
    public static interface Stream {
         InternalAggregation readResult(StreamInput in) throws IOException;
    }

    /**
     * Registers the given stream and associate it with the given types.
     *
     * @param stream    The streams to register
     * @param types     The types associated with the streams
     */
    public static synchronized void registerStream(Stream stream, BytesReference... types) {
        Map newStreams = new HashMap<>(streams);
        for (BytesReference type : types) {
            newStreams.put(type, stream);
        }
        streams = unmodifiableMap(newStreams);
    }

    /**
     * Returns the stream that is registered for the given type
     *
     * @param   type The given type
     * @return  The associated stream
     */
    public static Stream stream(BytesReference type) {
        return streams.get(type);
    }

}